The present invention relates generally to transluminal application of therapeutic cells for tissue repair, such as myocardial repair, and more particularly to balloon catheter protected transluminal application of multipotent (stem) cells for repair of a failing body organ such as heart, brain, liver, kidney or pancreas, and even related glands, nerves, and muscles. More specifically, the invention provides a novel method to repair failing tissue, and, in conjunction therewith, instrumentation and a method for the control of stem cell injection into the body.
The present invention involves considering parameters that determine conditions for injecting stem cells into a distinct area of the human body, and provides a method to achieve an adapted and titrated treatment form with respect to the various locations of stem cell injection, and also with respect to the different properties of the injected stem cells and the respective organ targeted for repair in an individual patient.
In principle, the human body has three types of cells: (1) cells that continuously undergo replication and reproduction, such as dermal cells and epithelial cells of the intestine, which have a life as short as ten days and are replaced by the same cell type in replication; (2) cells differentiated in the adult state, but having the potential to undergo replication and the ability to reenter the cell cycle under certain conditions, such as liver cells, which enable the liver to regrow and repair itself even if a major portion of the liver is removed; and (3) cells that stop dividing after they have reached their adult stage, such as neuro cells and myocardial cells.
For the latter type or group of cells, the number of cells in the body is determined shortly after birth. For example, myocardial cells stop dividing at about the 10th day after delivery, and a fixed number of myocardial cells remains for the rest of the human body's life. Changes in myocardial function occur not by division and new cell growth, but only as a result of hypertrophy of the cells.
Although the absence of cell division in myocardial cells is beneficial to prevent the occurrence of tumors—which practically never occur in the heart—it is detrimental to local repair capacities. During the individual's lifetime, myocardial cells are subjected to various causes of damage, which irreversibly lead to cell necrosis or apoptosis.
The primary reason for cell death in the myocardium is ischemic heart disease—in which the blood supply to the constantly beating heart is compromised through either arteriosclerotic build-up or acute occlusion of a vessel following a thrombus formation, generally characterized as myocardial infarction (MI). The ischemic tolerance of myocardial cells following the shut-off of the blood supply is in a range of three to six hours. After this time the overwhelming majority of cells undergoes cell death and is replaced by scar tissue.
Myocardial ischemia or infarction leads to irreversible loss of functional cardiac tissue with possible deterioration of pump function and death of the individual. It remains the leading cause of death in civilized countries. Occlusion of a coronary vessel leads to interruption of the blood supply of the dependent capillary system. After some 3 to 6 hours without nutrition and oxygen, cardiomyocytes die and undergo necrosis. An inflammation of the surrounding tissue occurs with invasion of inflammatory cells and phagocytosis of cell debris. A fibrotic scarring occurs, and the former contribution of this part of the heart to the contractile force is lost. The only way for the cardiac muscle to compensate for this kind of tissue loss is hypertrophy of the remaining cardiomyocytes (accumulation of cellular protein and contractile elements inside the cell), since the ability to replace dead heart tissue by means of hyperplasia (cell division of cardiomyocytes with formation of new cells) is lost shortly after the birth of mammals.
Other means of myocardial cell alteration are the so-called cardiomyopathies, which represent various different influences of damage to myocardial cells. Endocrine, metabolic (alcohol) or infectious (virus myocarditis) agents lead to cell death, with a consequently reduced myocardial function. The group of patients that suffer myocardial damage following cytostatic treatment for cancers such as breast or gastrointestinal or bone marrow cancers is increasing as well, attributable to cell necrosis and apoptosis from the cytostatic agents.
Prior to advances described in applicant's '860 patent and '403 application, the only means for repair has been to provide an optimal perfusion through the coronary arteries using either interventional cardiology—such as PTCA (percutaneous transluminal coronary angioplasty), balloon angioplasty or stent implantation—or surgical revascularization with bypass operation. Stunned and hibernating myocardial cells, i.e., cells that survive on a low energy level but are not contributing to the myocardial pumping function, may recover. But for cells that are already dead, there has been no recovery.
The current state of interventional cardiology is one of high standard. Progress in balloon material, guide wires, guiding catheters and the interventional cardiologist's experience as well as the use of concomitant medication such as inhibition of platelet function, has greatly improved the everyday practice of cardiology. But an acute MI remains an event that, even with optimal treatment today, leads to a loss of from 25 to 100% of the area at risk—i.e., the myocardium dependent on blood supply via the vessel that is blocked by an acute thrombus formation. Complete re-canalization by interventional means is feasible, but the ischemic tolerance of the myocardium is the limiting factor.
An article published in 2000 (Schömig A. et al., “Coronary stenting plus platelet glycoprotein IIb/IIIa blockade compared with tissue plasminogen activator in acute myocardial infarction,” N Engl J Med 2000; 343:385-391), reports on a study, for which the applicant herein was a clinical investigator, of the myocardial salvage following re-canalization in patients with an acute MI. The average time until admission to the hospital was 2.5 hours and complete re-canalization was feasible after 215 minutes, about 3.5 hours. Still, only 57% of the myocardium at risk could be salvaged by re-canalization through interventional cardiology by means of a balloon and stent. When the group of patients was randomized to classical thrombolytic therapy—the worldwide standard (no interventional means)—only 26% of the myocardium at risk could be salvaged. Thus, even under optimal circumstances more than 40% of the myocardial cells are irreversibly lost. Many patients arrive at hospital 6-72 hours after acute symptoms of vessel blockage by a thrombus, so the average loss of affected myocardial tissue is assumed to range from 75-90% after acute MI.
Cells can survive on a lower energy level, referred to as hibernating and stunning myocardium, so as collateral blood flow increases or re-canalization provides new blood supply they can recover their contractile function. The principle of myocardial reperfusion, limitation of infarct size, reduction of left ventricular dysfunction and their effect on survival are described by Braunwald et al. in “Myocardial reperfusion, limitation of infarct size, reduction of left ventricular dysfunction, and improved survival: should the paradigm be expanded?,” Circulation 1989; 79:441-4.
Annually, about five million Americans survive an acute MI. Clearly then, loss of affected myocardial tissue is a problem of major clinical importance. Currently, repair is limited to hypertrophy of the remaining myocardium, and optimal medical treatment by a reduction in pre- and after-load as well as the optimal treatment of the ischemic balance by β-blockers, nitrates, calcium antagonist, and ACE inhibitors.
Replacement of the dead myocardium (scar tissue) by re-growing cells is expected to have a profound impact on the quality of life of affected patients.
In addition to ischemic heart disease, among other causes for the reduction of myocardial cells that contribute to pumping or electrical function of the heart are the cardiomyopathies, which describe a certain dysfunction of the heart. Reasons include chronic hypertension that ultimately leads to a loss in effective pumping cells, and chronic toxic noxious such as alcohol abuse or myocarditis primarily following a viral infection. Also, cell damage in conjunction with cytostatic drug treatment is becoming of greater clinical relevance. The contracting myocardium becomes affected, as well as the conduction system of the heart. Clinical symptoms are slow or fast heart rates, generally called sinus node disease, AV Block conduction block and re-entry tachycardias and atrial flutter, atrial fibrillation, ventricular tachycardias and ventricular fibrillation.
In their initial report (Goldstein M. A. et al., “DNA synthesis and mitosis in well-differentiated mammalian cardiocytes,” Science 1974; 183:212-3), the group of William C. Claycomb et al., which has engaged in research on the behavior and development of myocytes since the early 1970's, described the incorporation of 3H-Thymidin into the nuclei of heart cells of two days old rats which indicates that neonatal cardiac cells still undergo synthesis of DNA and divide despite the presence of contractile proteins. This phenomenon of cell division ceases at day 17 of the postnatal development. After that time no further division of cardiac cells occurs, either in rats or in humans.
The interest in mammalian cardiomyocytes has led to the development of cultures of adult cardiac muscle cells (Claycomb W. C. et al., “Culture of the terminally differentiated adult cardiac muscle cell: A light and scanning electron microscope study,” Dev Biol 1980; 80:466-482), and ultimately to the generation of a transplantable cardiac tumor-derived transgenic AT1-cell.
During the 1980's studies were conducted with the characterization of this atrial derived myocyte cell line, which is immortalized by the introduction of the SV40-large-T-oncogene (SV40-T). From this AT-1-cell-group, other adult cardiomyocytes have been derived, described as HL-1-cells, which can be passaged indefinitely in culture, recovered from a frozen stock, retain a differentiated cardiomyocyte phenotype, and maintain their contractile activity. Among the references are Delcarpio J. B. et al., “Morphological characterization of cardiomyocytes isolated from a trans-plantable cardiac tumor derived from transgenic mouse atria (AT-1 cells),” Circ Res 1991; 69(6):1591-1600; Lanson Jr. N. A. et al., “Gene expression and atrial natriuretic factor processing and secretion in cultured AT-1 cardiac myocytes,” Circulation 1992; 85(5):1835-1841; Kline R. P. et al., “Spontaneous activity in transgenic mouse heart: Comparison of primary atrial tumor with cultured AT-1 atrial myocytes,” J Cardiovasc Electrophysiol 1993; 4 (6):642-660; Borisov A. B. et al., “Proliferative potential and differentiated characteristics of cultured cardiac muscle cells expressing the SV 40 T oncogene,” Card Growth Reg 1995; 752:80-91; and Claycomb W. C. et al., “HL-1 cells: A cardiac muscle cell line that contracts and retains phenotypic characteristics of the adult cardiomyocyte,” Proc Natl Acad Sci USA 1998; 95:2979-84.
Cardiomyocyte transplantation in a porcine MI model has been studied intensively in collaboration with the research group of Frank Smart (Watanabe E. et al., “Cardiomyocyte transplantation in a porcine myocardial infarction model,” Cell Transplant 1998; 7(3):239-246). In conjunction with AT-1 cardiomyocytes, human fetal cardiomyocytes were injected through a syringe and needle into the adult pig heart infarction area.
In summary, these cells showed local growth and survived in the infarction border zone, but could not be found in the core scar tissue of the myocardial infarction. The majority of the implanted cells were replaced with inflammatory cells, suggesting that the immuno-suppressant regimen that was concomitantly applied was not sufficient for the grafted cells to survive in the host myocardium. Other factors that may have influenced the result that the transplanted cells were not detected, could possibly be linked to the fact that the cells were grafted 45 days after inducing the infarction.
It is known that the inflammatory stimuli for cell growth are significantly reduced in the first two to three weeks of an MI. Also, that transforming-growth-factor-b (TGF-b), fibroblast-growth-factor-2 (FGF-2), platelet-derived-growth-factor (PDGF) and other cytokines, like the interleucin-family, tumor-necrosis-factor-a (TNF-a) and interferon-gamma are strong stimulators of cell proliferation and cell growth. The adjunct therapy with immuno-suppression has further reduced these stimuli for cell growth.
Another major factor for the failure of detection of grafted cells in the myocardial scar may be the selection of the infarction model. An artery is occluded and the blood supply has not recovered before grafting. There is no reason to assume that the grafted cells could survive in an ischemic area and grow, better than the myocytes.
Therefore, other groups have tried to induce a myocardial angiogenesis by gene-therapy. This was either performed by the administration by fibroblast growth factor II in the presence or absence of heparin (see Watanabe E. et al., “Effect of basic fibroblast growth factor on angiogenesis in the infarcted porcine heart,” Basic Res Cardiol 1998; 93:30-7) or by application of vascular endothelial growth factor (VEGF), a potent mitogen for endothelial cells. VEGF stimulates capillary formation and increases vascular permeability (Lee J. S. et al., “Gene therapy for therapeutic myocardial angiogenesis: A promising synthesis of two emerging technologies,” Nat Med 1998; 4 (6):739-42). Still other groups have tried to increase the collateral capillary blood flow by human bone marrow derived angioblasts and have shown an improvement in acute myocardial infarction in rats treated with injections of colony-stimulating-factor-G (CSF-G) mobilized adult human CD-34 cells (Kocher A. A. et al., “Neovascularization of ischemic myocardium by human bone-marrow-derived angioblasts prevents cardiomyocyte apoptosis, reduces re-modeling and improves cardiac function,” Nat Med 2001; 7 (4):430-6).
While these approaches certainly have some research merit, their clinical relevance for the majority of patients is not as important, since we have effective means to re-canalize an occluded vessel and provide a blood supply via the natural branching of the coronary arteries, which further subdivides into arterioles and capillaries.
Other attempts to transplant preformed patches also necessitate the growth of the grafted cells in a patch formation and a surgical operation in a patient, which requires opening the thoracic cage.
Considering the complications, the cost and the risk associated with these time consuming procedures, it becomes clear that they offer only limited likelihood for widespread routine application.
Other groups have tried to make use of the precursor cells that are found in the peripheral muscle. Unlike the heart, there is a certain degree of repair in peripheral skeletal muscles, since the peripheral skeletal muscle contains progenitor cells, which have the capability to divide and replace the peripheral muscle. By isolating those cells from a probe of a thigh muscle, the progenitor cells of skeletal muscle have been separated, cultured and re-injected in an animal model (Taylor D. A. et al., “Regenerating functional myocardium: Improved performance after skeletal myoblast transplantation,” Nat Med 1998; 4 (8):929-33; Scorsin M. et al., “Comparison of the effects of fetal cardiomyocyte and skeletal myoblast transplantation on postinfarction left ventricular function,” J Thorac Cardiovasc Surg 2000; 119:1169-75), and more recently in some patients also.
The application of these cultured cells has also been attempted by injection with small needles following an opening of the subject's chest and the pericardial sac. While in the model of kryo-infarction, in which only the myocardial cells die but the blood supply through the vascular system is not limited, the injection of autologous skeletal myoblasts improves the myocardial function. The results indicated, however, that the engrafted cells retain skeletal muscle characteristic, which means they cannot contract at the constant fast rate imposed by the surrounding cardiac tissue. In addition, no electrical connection exists between the graft cells and the host tissue, and it is assumed that their contribution to improve contractile performance probably resulted from the mechanical ability of the engrafted contractile tissue to respond to stretch activation by contraction.
Considering the experience with latissimus dorsi muscle grafting—a procedure called dynamic cardiomyoblasty—, disappointing results with the possible use of skeletal muscle as a myocardial substitute indicate that the long term different muscle characteristics of skeletal muscles do not match the need of a constantly pumping myocardial cell. Therefore, these cells might achieve at best improving the quality of the scar of the ischemic myocardium, but not actively contributing long term to a contraction of this area.
The disclosure of the '403 application is directed to interventional medicine through an intraluminal application of cells that have the capability to replace the necrotic tissue of a failing organ, such as the heart in the case of a MI, to resume the myocardial function and therefore improve the pumping performance of the myocardium.
The procedure is oriented on the clinical practice of interventional cardiology following the principle that only those approaches that are both (a) relatively easy to perform, with little or no risk to the patient but a potentially high benefit, and (b) highly cost effective, are likely to be routinely applied in everyday medicine.
An important aspect of the invention described in the '403 application is that the cells to be used in the intraluminal or transluminal application preferably are autologous adult stem cells, which are derived from the same patient that has suffered the infarction. The cells are harvested and separated before injection, from the same individual (autologous transplantation). In a case of failing tissue of the myocardium, these cells are then injected into the coronary artery that caused the infarction or into the corresponding coronary vein in a retrograde manner.
The approach taken there recognizes the need to give stem cells a certain contact time to adhere and migrate from the vascular bed into the infarcted myocardial area. In contrast to previous approaches, in which patches or applications through needles into the infarcted area have been considered, the inventive approach hypothesizes that the most effective way to deliver the cells to the infarcted area is through the vascular tree of coronary arteries, arterioles and capillaries that supply the infarcted area. An occlusion balloon of an over the wire type catheter is inflated at the site of the primary infarction, after the vessel has been re-canalized and the blood flow reconstituted.
While the blood flow is still blocked, the stem cells are supplied by slow application through the balloon catheter over a relatively short period of time, 10 to 15 minutes, for example. That is, the stem cells are injected through the inner lumen of the catheter while the balloon is inflated, and therefore, no washout occurs. This intracoronary, intravascular, intraluminal, or transcoronary application of cells during a period that flow or perfusion is ceased is believed to be critical to enabling the cells to successfully attach to the myocardial wall. And further, to overcome more actively the endothelial barrier following the increased pressure in the vascular bed or duct, which is attributable to the retrograde flow of cells being limited through the inflated balloon catheter.
These principles of that invention are not limited to cellular repair of damaged or failing myocardial tissue, but may be applied in processes for repair of tissue of various organs of the body, additionally including the brain, liver, kidney, pancreas, lungs, related glands, nerves, and muscles, for example, by intraluminal application of the stem cells through an appropriately designated vessel or duct leading to the targeted tissue.
Thus, according to the invention of the '403 application, a method for repairing tissue of an organ in a patient's body includes delivering adult stem cells that have the capability to replace tissue of a failing organ to the site of the tissue to be repaired, by an intraluminal application through a blood vessel of or duct to the site, and occluding the blood vessel or duct proximal to the location of cell entry therein via the intraluminal application during at least a portion of the duration of the cell delivery to increase the concentration of cells delivered to the site. A balloon catheter is preferred for the intraluminal application, and the occlusion is performed by inflating the balloon of the catheter for a time interval prescribed to increase the concentration of cells delivered to the site. Initially, a guide wire is introduced through the vessel or duct to the site, to allow the catheter to be advanced over the wire until the distal end reaches the vicinity of the target site for delivery of the stem cells.
The autologous adult cells utilized for that method may be harvested from the patient's own body, such as from the bone marrow, adipose tissue, or may originate from lipoaspirate. Harvesting should be within a short time interval immediately prior to delivery of the cells to the organ site to enhance the likelihood of successful organ repair.
It had been hypothesized by most researchers that adult stem cells are tissue specific and that a certain stem cell-like population exists in every organ and is capable of differentiation into this certain tissue with exceptions to this rule regarding repair in heart and brain. Studies reported in and after the year 2000 indicated an underestimated potential of these cells. It was shown that murine and human neural stem cells (NSC) give rise to skeletal muscle after local injection (see, for example, Galli R et al., “Skeletal myogenic potential of human and mouse neural stem cells,” Nat Neurosci 2000;3:986-991). Bone marrow stem cells have were shown to replace heart tissue (cardiomyocytes, endothelium and vascular smooth muscle cells) after injection into lethally irradiated mice with a myocardial infarction (see Jackson K. A. et al., “Regeneration of ischemic cardiac muscle and vascular endothelium by adult stem cells,” J Clin Invest 2001;107(11):11395-402). The tissue damage in general appears to transmit signals which direct multi-potential stem cells to the site of destruction, and these precursors undergo a multi-step process of migration and differentiation at the organ site to replace damaged cells in form and function.
Experiments with cultured fetal cardiac myocytes or neonatal myocytes impose limitations owing to their heterologous nature and their possible induction of an immuno response necessitating an immuno-suppressive therapy. Complications and risks associated with an immuno-suppressant therapy are an increased susceptibility to infection and the possible development of malignancies. In addition, it was speculated that only a few patients would be willing to undergo a long term immuno-suppressive therapy with all its negative side effects.
An alternative approach by Prockop suggested that marrow stromal cells act as stem cells for non hematopoetic tissue, capable to differentiate into various types of cells including bone, muscle, fat, hyaline cartilage and myocytes (Prockop D. J. et al., “Marrow stromal cells for non hematopoetic stem tissues,” Science 1997; 276:71-74).
Findings reported since 2000 piqued interest in adult cardiomyocytes. A report in Nature describes the ability to inject adult bone marrow stem cells from transgenic mice into the border of infarcted myocardial tissue (Orlic D. et al., “Bone marrow cells regenerate infarcted myocardium,” Nature 2001; 410:701-5). According to this report, these adult stem cells are capable of differentiation into cardiomyoblasts, smooth muscle cells and endothelial cells after injection. The infarcted myocardium implied that the transplanted cells responded to signals from the injured myocardium which promoted their migration, proliferation and differentiation within the necrotic area of the ventricular wall.
The classical way to recover adult stem cells is a bone marrow tap. The bone marrow contains a wide variety of hematopoetic and mesenchymal stem cells in addition to the T-lymphocytes, macrophages, granulocytes and erythrocytes. By incubation with monoclonal antibodies specific for the respective cell lineages and by sorting and removing with a biomagnet after incubation with magnetic beads and cell sorting with FACS (fluoroscopy activated cell sorting), a highly enriched cell line of bone marrow derived stem cells can be insulated, cultured and grown.
A subsequent report indicated that cells from human adipose tissue contain a large degree of mesenchymal stem cells capable of differentiating into different tissues in the presence of lineage specific induction factors including differentiation into myogenic cells (see Zuk P. A. et al., “Multilineage cells from human adipose tissue: Implications for cell-based therapies,” Tiss Engin 2001; 7(2):211-28). The interesting approach in this research was that out of a lipoaspirate of 300 cm3 from the subcutaneous tissue, an average of 2-6×108 cells can be recovered. Even if one assumed that after processing of this liposuction tissue and separation and isolation of the mesenchymal stem cells, only 10% of these stem cells might be left for culture, the remaining approximately 107 (10 million) cells would be quite sufficient to be used for the intraluminal or transluminal transplantation process.
The latter approach appeared to benefit by avoiding culture and passaging of the stem cells. This is important, since in the early phases of MI high activity of inflammatory cytokines promote adhesion, migration and proliferation of the stem cells. In addition, as long as no scar core tissue is formed it is much easier for these cells to migrate into the whole area of myocardial infarction and resume the cardiac function.
More recently, embryonic stem cells became the subject of intensive discussion, particularly their pluripotency to differentiate into a vast range of tissues and organs of the human body that are in need for repair. The discussion has included the potential use of such stem cells for replacement of insulin producing cells as well as embryonic stem cells that can differentiate into cells with structural and functional properties of cardiomyocytes. See, for example, Kehat I. et al., “Human embryonic stem cells can differentiate into myocytes with structural and functional properties of cardiomyocytes,” J Clin Invest 2001; 108:407-14. Earlier, the proliferation of embryonic stem cells was elegantly described in principle in Klug M. G. et al., “Genetically selected cardiomyocytes from differentiating embryonic stem cells form stable intracardiac grafts,” J Clin Invest 1996; 98(1):216-24. The latter group succeeded in plating a cell line following a fusion gene consisting of the a—cardiac-myocyte-heavy-chain-promotor and the c-DNA encoding aminoglycoside-phosphotransferase that was stably transfected into pluripotent embryonic stem cells. The resulting cell lines were differentiated in vitro and subjected to a G418 selection. The selected cardiomyocyte cultures were 99.6% pure and highly differentiated.
It is important to consider the engraftment of pluripotent embryonic stem cells into a failing organ, but also the possibility of resulting tumor formation. Therefore, pluripotent embryonic stem cells need to be cultured in an undifferentiated status, transfected via electroporation and grown in differentiated cultures. The interesting approach in this work is the high yield of selected embryonic stem cell derived cardiomyocytes which, with simple genetic manipulation, can be used to produce pure cultures of cardiomyocytes. It has also been reported that isolation of primate embryonic stem cells with cardiogenic differentiation is feasible (Thomson J. A. et al., “Isolation of a primate embryonic stem cell,” Proc Natl. Acad Sci USA 1995; 92:7844-48).
In addition, it was reported that human cardiomyocytes can be generated from marrow stromal cells in vitro as well, but with a low yield of differentiated myocytes (Makino S. et al., “Cardiomyocytes can be generated from marrow stromal cells in vitro,” J Clin Invest 1999; 103:697-705). The 1997 Prockop report (supra) in Science describes another line of cardiomyocytes generated from marrow stromal cells in vitro. This cardiomyogenic cell line was derived from murine bone marrow stromal cells that were immortalized and treated with 5-azacytidine. By mechanically separating spontaneously beating cells, a cell line was isolated that resembled a structure of fetal ventricular cardiomyocytes expressing iso-forms of contractile protein genes such as alpha cardiomyocyte heavy chain, -light chain, a-actin, Nkx2.5-Csx, GATA-4, tef-1, MEF-2a and MEF-2D.
While these embryonic stem cells provide optimism for the future that cardiomyocytes derived from embryonic cells might fulfill the requirements of cells that can (a) be passaged indefinitely in culture, (b) be recovered from frozen stocks and are readily available if a patient with a myocardial infarction comes to the cath lab, (c) retain their differentiated cardiomyocyte phenotype and (d) maintain contractile activity with minimum or no immunogenity, further basic research is needed before they can be applied in the animal model. It is likely that a primate model of infarction and the transplantation of primate embryonic stem cell derived cardiomyocytes may be needed as the final proof of principle before a human study might be conducted.
For ethical, immunological and feasibility reasons, the applicant's 403 application proposed transplantation of autologous adult stem cells to be the most straightforward and practical approach to repair failing myocardium. The process of that application promotes invasion of ischemically injured cardiac tissue by stem cells that firmly attach and subsequently undergo differentiation into beating cardiomyocytes that are mechanically and electrically linked to adjacent healthy host myocardium. Adhesion of the injected stem cells and their migration beyond the endothelial barrier may be confirmed by observation after several days of frozen sections using light microscopy and, subsequently, electron microscopy. For evidence of the transition of stem cells into cardiomyocytes, markers are introduced into the stem cells before they are re-injected into the myocardial tissue to be repaired.
One proposal was to transplant male cells carrying the Y-chromosome into a female organism, but at least two factors weigh against this. It could lead to immunologic problems because of the different cell surfaces carried by the recipient and the donor (heterologous transplant), a potential reason that some studies are not able to show a successful heterologous cell transplantation. More importantly, a predominance of inflammatory cells exists at the site of myocardial injury, which leads to an immediate recognition of foreign cell surface proteins with consequent elimination of the cells. Use of autologous stem cells would not carry this immunologic risk of cell destruction, although some difficulty is encountered in prior introduction of genetic or protein markers into those cells.
To overcome this difficulty, a green fluorescence protein (GFP) was used as a marker, with introduction into the stem cell genome by liposomal gene transfer. Cells can then be identified after transplantation by fluorescence microscopy. As part of the procedure, stem cells are also marked by 3H-Thymidin, a radioactive labeled part of DNA. All stem cells undergoing DNA replication for mitosis will introduce 3H-Thymidin into their genome, and thus can be detected afterwards by gamma count. One limitation of this process is the fact that radioactivity (per volume) declines with each subsequent cell division (albeit initial total radioactivity stays constant). Nevertheless, this marker aids in developing a gross estimate of the amount of cells in a certain organ or tissue (e.g., heart, spleen, liver etc.).
Referring to FIG. 1, taken from the '403 application, subcutaneous adipose tissue 20 is obtained from a liposuction procedure on a patient 1 during local anesthesia. A hollow canule 21 is introduced into the subcutaneous space through a small cut. Gentle suction by a syringe 22 as the canule is moved through the adipose compartment mechanically disrupts fat tissue. Following a normal saline solution and a vasoconstrictor epinephrine, a lipoaspirate of 300 cc. is recovered within the syringe, and is processed immediately to obtain a high density cellular pellet. Following filtration to remove cellular debris, the cells are ready to be injected into the area of interest in the patient's body.
Referring to FIG. 2, also from the '403 application, as well as to FIG. 1, the recovered autologous adult stem cells are transplanted in the donor patient by intracoronary or transcoronary application for myocardial repair. A balloon catheter 11 is introduced into the cardiovascular system at the patient's groin 3 using an introducer 4, and through a guiding catheter 5 over a guide wire 18 into the aorta 6 and the orifice 7 of a coronary artery 8 of the heart 2 at or in the vicinity of the site where failed tissue, e.g., from an infarction, is to be repaired. The failed tissue is supplied with blood through artery 8 and its distal branches 9 and 10. The cells are hand injected or injected through the inner lumen 12 of the balloon catheter 11 by a motor driven constant speed injection syringe 16 and connecting catheter 17 to an entry point of the central lumen at the proximal end of catheter 11. The exit point of the central lumen 12 is at the distal end of catheter 11 which has been advanced into the coronary artery 8 in proximity to the site of the desired repair. The cells 15 are delivered to this site by means of slow infusion over 15-30 minutes, for example.
Normally anything inside the blood vessel, including these cells, is separated from the parenchymatous organ or the tissue outside the vessel. Blood flows through the larger arteries into the smaller arteries, into the arterials, into the capillaries, and then into the venous system back into the systemic circulation. Normally, the cells would be prevented from contacting the tissue to be repaired because of the endothelial lining and layer of the vessel that protects the tissue. But under certain circumstances this barrier is overcome, and the cells can attach to the inside of the vessel, migrate and proliferate in the adjacent tissue. These circumstances are facilitated in the case of situations of acute inflammation such as an acute myocardial infarction, and the increased pressure in the injection system promotes the injected cells to overcome the barrier.
The endothelial ischemic damage owing to the infarction allows white blood cells, especially granulocytes and macrophages, to attach via integrins to the endothelial layer. The endothelial layer itself is dissolved in places by release of hydrogen peroxide (H2O2) which originates from the granulocytes. This mechanism produces gaps in the endothelial layer that allow the stem cells to dock to the endothelial integrins and also to migrate through these gaps into the tissue to be repaired. An adjacent factor that enables the stem cells to migrate into the organ tissue is referred to as a stem cell factor that acts as a chemo-attractant to the cells.
A sufficient quantity of the repair cells must be allowed to migrate into contact with the failing tissue to achieve a high number of transplanted cells in the tissue. This is the principal reason for using a balloon catheter 11 or some other mechanism that will allow the physician to selectively block the antegrade blood flow and the retrograde stem cell flow. In the process, the balloon 14 of catheter 11 is inflated with biocompatible fluid through a separate lumen 13 of catheter 11 to occlude coronary artery 8 and its distal branches 9 and 10, thereby causing perfusion through the vessel to cease. The balloon is inflated immediately before or upon injection of the stem cells through the inner lumen of the catheter, and maintained throughout the period of injection. This enables the desired large number of adhesions of the cells 15 to the failing tissue to be achieved. The absence of blood flow at the critical site of this tissue to be repaired prevents what would otherwise result in a retrograde loss of injected cells, an inability to increase the pressure at the injection site to overcome the endothelial barrier and to force the cells through the gap, and an antegrade dilution with blood flow of the cells being injected to that location through the catheter 11.
Depending on the type and number of cells delivered, the blockage is maintained for a relatively short period of time, e.g., on the order of 1-15 minutes, sufficient to allow a high concentration and considerable number of cell attachments to the tissue at the designated site, to achieve a successful repair. The balloon is deflated, and the balloon catheter is removed from the patient following the designated period.
The invention of the '403 application uses the natural distribution tree of the arterioles and the capillaries, provided that the transplanted cells can overcome the endothelial barrier and migrate into the tissue, and interventional cardiology means can restore blood flow into the infarcted area again.
In clinical practice there is a 96% success rate with interventional cardiology to restore blood flow following an acute MI after an occlusion of a coronary artery. Since venously injected stem cells can be found in the myocardium, and in an acute MI the endothelial barrier is considerably damaged, it may be concluded that a local injection into the infarcted area with an occlusive balloon to prevent a washout of the cells is a highly desirable approach. In studies performed in the past with a technique called ‘BOILER’-lysis, older venous bypass grafts were occluded by a thrombus that has grown over a prolonged period of time, and it was observed that an acute injection of a thrombolytic agent rarely dissolved these old thrombi. But after an over the wire balloon catheter was inserted into the occluded graft, a prolonged application of a thrombolytic substance such as urokinase was successful in achieving thrombolysis. The agent is injected at the tip of the balloon catheter, and is forced antegradely into the thrombus. The inflated balloon prevents a washout by the normal coronary circulation and allows the injection at a defined volume per time.
The process of the '403 application may be applied to the brain in the case of a patient having suffered a cerebral damage such as an infarction. Previous studies indicated that stem cells have the capacity to replace neural cells in the brain and overturn the consequences of an acute vascular stroke. The injection catheter would be advanced to the site of the damaged tissue through an appropriate arterial path into the applicable region of the patient's brain. Blockage of blood flow in this case would add a period (e.g., minutes) of limited blood supply but would enable the cells to overcome the endothelial barrier.
Other body organs having damaged tissue to be repaired by variations of this process include the pancreas, the liver, and the kidneys. The pancreas has a duct (the ductus Wirsungii) through which pancreatic enzymes are delivered into the intestines, and which can be accessed in a retrograde manner by endoscopic retrograde choledocho-pancreaticography (ERCP). Failing tissue in the case of a diabetic patient means that the pancreatic cells therein no longer produce sufficient insulin for the patient's needs. By visual guidance through a small fiberglass instrument a small balloon catheter is introduced into this duct, and the balloon inflated to occlude the duct during delivery of stem cells through the catheter to the site of the damaged tissue, so as to prevent the injected cells from being washed out into the intestines, to enhance large scale adhesions and penetration of the cells to the target tissue.
An analogous procedure is used for repair of damaged tissue of the liver, through the bile duct system. The normal bile duct barrier is overcome with pressure that can be generated if the balloon is inflated while the cells are slowly injected. The pressure distally of the injection site increases as more and more cells are injected. Repair of failing tissue in the kidney(s) from renal infarction is achieved by an analogous procedure.
The '403 application also describes a process to open up the blood circulation in an ischemic organ and, to inject stem cells for repair of tissue damage in the organ occasioned by prior blockage. In a myocardial infarction, for example, only a portion of the myocardial cells that had been ischemic will survive. A typical procedure is to perform a balloon angioplasty of the blocked artery, followed by implanting a stent at the site of the lesion. But even in the case of optimal treatment some 40% of the affected cells will die. To reduce this effect, autologous adult stem cells are injected into the organ proximate the site of the target tissue for repair thereof within a predetermined brief period after opening the ischemic organ to circulation of blood flow.
Referring to FIG. 3, also taken from the '403 application, in a method for delivery of stem cells through a balloon catheter to the anterior cerebral circulation in a patient 31, an introducer sheath 33 is advanced through the right groin 32, and a balloon double lumen catheter 34 is advanced through introducer sheath 33 and over a guide wire 48 placed in the artery of interest. The proximal end of guide wire 48 is left to project from opening 35a of catheter 34. A side branch opening 35b of catheter 34 is operatively coupled through an inflation lumen of the catheter for selective inflation and deflation of its balloon 46.
Guide wire 48 is advanced through the central lumen of catheter 34, and the catheter is then maneuvered to the selected site over the guide wire through iliac artery 37, abdominal and thoracic aorta 38, aortic arch 39, and into the right carotid artery 40 beyond the branching of the vessels 41 for the right arm. Alternatively, the guide wire and catheter are advanced to a location in the left carotid artery 42, which either originates after the branch-off of the left subclavian artery 43, or directly from the aortic arch 39 where the left subclavian artery originates from a separate orifice.
The guide wire is advanced through the common carotid artery into the right internal carotid artery 40 and into the proximal circulation of the Circulus Willisi 44, to encounter the anterior cerebral artery 45 at its origination. Catheter 34 is then advanced to position its tip 47 and balloon 46 in the anterior cerebral artery 45, with the catheter tip located at the site for delivery of the harvested autologous adult stem cells, and guide wire 48 is removed. The opening 35a of the same lumen used for the guide wire is now available for injecting stem cells for delivery to that site.
Referring also to FIGS. 3A and 3B, the conus 50 of a syringe 49 (FIG. 3A) is connected to port 35a of catheter 34, and the conus 53 of another syringe 52 (FIG. 3B) is connected to the inflation port 35b of catheter 34. Port 35b operates through the inflation lumen for balloon 46 of catheter 34. Syringe 52 is of small size and includes a pressure gauge 55 to measure the applied pressure as the fluid 54 within the syringe is expelled into port 35b to inflate balloon 46 to a low pressure of 0.5 to 0.8 atm. This pressure is sufficient to tightly seal the vessel (anterior cerebral artery 45) at the location of the balloon. To assist in recognizing a possible rupture of balloon 46, the fluid 54 in syringe 52 is a 50/50 mixture of saline and contrast dye. Balloon 46 may be deflated on completion of the procedure or in an emergency by withdrawing the fluid 54 back into syringe 52.
While anterior cerebral artery 45 is tightly sealed toward its proximal end 44, stem cells 51 within syringe 49 are slowly ejected from conus 50 into port 35a of the catheter. The stem cells travel through the central lumen of catheter 34 formerly occupied by guide wire 48 and exit the lumen at the site of catheter tip 47. The stem cells thus enter into the cerebral circulation at that site. The very brief period of limited blood supply during blockage of blood flow through artery 45 by inflated balloon 46 is sufficient for the stem cells to overcome the endothelial barrier but not enough to cause injury to the brain.
For treating a diseased kidney, stem cells are introduced similarly through a catheter navigated over a guide wire in the patient's right groin into the iliac artery 37, the abdominal aorta 38, the applicable renal artery 57, and the diseased kidney 58.
FIG. 4, also taken from the '403 application, illustrates a method for delivery of stem cells through a natural duct in a patient 61. In this procedure, an endoscope 64 is advanced through the mouth 62 and esophagus 63 of the patient. The endoscope 64 is flexible, and designed and implemented with a plurality of channels including a visualization and fiber optics channel 65, flushing channel 66, side port open channel 67, and working channel 68. The distal tip 75 of endoscope 64 is readily bendable to allow it to be advanced through a tortuous path. The endoscope 64 is advanced from the esophagus 63 through the diaphragm 70, through the stomach 69, and until its distal tip is located in the duodenum 71.
If the pancreas is to be repaired, the distal tip is positioned such that a side port 72 of the endoscope is aligned for entry into the ductus Wirsungii 76, which supports the internal structure of the pancreas 73 with all its side branches. Proper alignment is verified through visualization and fiber optics channel 65 of endoscope 64. Then, a small balloon guided catheter 77 is advanced over a guide wire 78 threaded through the side port open channel 67 and out of the side port 72 into the ductus Wirsungii.
Stem cells are delivered and the balloon is inflated by syringes in a method similar to that described with respect to FIGS. 3A and 3B. The distal tip of the catheter is advanced through channel 67 of the endoscope 64 and out of the side port 72 to the site of the pancreatic tissue to be repaired. The catheter's balloon is then inflated through the inflation lumen of the catheter to occlude the Wirsungii duct while stem cells are introduced into the pancreatic tissue through the central lumen of the catheter by proper positioning of the catheter's distal tip at the site of the damaged tissue. Occlusion of the duct prevents stem cells from washing into the intestines, to enhance penetration of cells to the target tissue and large scale adhesions.
If the patient's liver 82 is to be repaired by delivery of stem cells through a natural duct, the distal tip 75 of endoscope 64 is positioned in the duodenum 71 to align its side port 72 for entry into the common biliary duct 80 that supports the liver and the gall bladder 81. Alternatively, the side branch of the bile duct may be used. The guide wire and balloon catheter are fed through channel 67 and out of side port 72 of the endoscope, into the duct. The distal tip of the catheter is positioned at the target site of the liver tissue, the guide wire is removed, and the catheter's balloon is inflated to occlude the biliary duct during introduction of stem cells for adhesion to and engraftment at the failing liver tissue.
The applicants herein have found that the quantity of stem cells required to be injected into the capillary bed is critical to obtaining optimal results. Experiments performed by the applicants have shown that the mean diameter of stem cells derived from subcutaneous adipose tissue is in a range of 11-12 microns. However, this cell size is larger than the size of the capillary bed, which ranges between 5-7 microns. It is essential that stem cells injected to reach a target organ site remain locally and engraft and migrate or cross the intraluminal endothelial lining and become incorporated into the failing tissue of the organ to be repaired.